This invention relates to blood collection methods, and to apparatus for use therewith, in which venous blood is collected from blood donors and in which one or more blood samples are collected for analysis.
It is imperative that the taking of samples during donation is done in such a way that contamination of the collected blood cannot occur through the process of sample collection. This rules out the use of tubular sampling ports and their associated vacuum phials, the use of pierceable or pre-slit septum ports, and the use of hypodermic needles to draw off samples from the blood line during donation, it being thereby possible for bacteria to be introduced into the blood flowing to the collection bag. Accordingly, it is standard practice to take samples after the desired amount of blood has been collected and after the line to the collection bags has been sealed. Samples can then be taken, using sampling ports, piercing the blood-line with a sampling needle or by dripping blood into open collection phials at any point between the IV needle (that is still in the donor""s vein) and the point at which the line has been sealed.
Examples of known blood sampling methods in blood collection procedures are provided in the disclosure of U.S. Pat. No. 4,786,286 by Baxter International Inc. This publication, and that of WO 94/12093 also by Baxter, further disclose the use of in-line containers of various designs for blood sample collection after blood collection has been completed. In WO 90/12606, Baxter discloses the use of pre-slit septum ports for blood sampling during infusion techniques (but not during blood donation procedures). Other in-line sampling ports are disclosed by Spacelabs Inc in European patent publication No. 0 376 168.
Despite careful precautions to avoid contamination in blood collection procedures, a small percentage of blood packs become contaminated with bacteria. It is becoming recognised that, despite the use of topical disinfectants prior to puncture, contamination can occur by the inclusion of bacteria from the skin of the donor at the puncture site. The literature suggests that, in rare cases, a hollow vena-puncture needle can cut a xe2x80x98plugxe2x80x99 of skin from the donor""s arm and that this plug may be carried into the collection bag along with the blood. It is postulated that the thickness of the plug is sufficient to protect bacteria within or just below the epidermis from the effects of the topical bactericide so that contamination of a blood pack can occur.
Besides not being wholly effective in preventing blood-pack contamination, the sampling procedures indicated above extend the duration of the collection procedure and the period during which the IV needle is in place in the patient""s arm. This is because sample collection must be effected after the full unit of blood has been collected and the blood line has been sealed.
U.S. Pat. No. 3,654,924 to Wilson et al. teaches the use of a flow-through sample pouch formed around a portion of the blood line that includes a frangible connection so that, if a sample is required, the connection can be broken and blood allowed to flow into the sample pouch. U.S. Pat. No. 5,167,656 to Lynn also teaches the use of a flow-through sample-pouch but omits the use of the frangible connection in the blood line. Lynn""s pouch fills with blood as blood flows to the bag-set and, after a unit of blood has been collected in the set, the line up-stream and down-stream from the pouch is sealed and the IV needle is withdrawn. Samples of blood may then be taken from the pouch. The use of such flow through pouches has the advantage that the procedure is shorter for the donor because samples can be taken from the pouch after the needle is removed from the donor""s arm. However, the procedure is not significantly shortened from the standpoint of the phlebotomist who must still wait until collection is finished and the blood line has been sealed before taking samples. More importantly, it is highly likely that any skin plug in the initial flow of blood will be carried through the sample pouch and into the collection bag.
U.S. Pat. No. 4,056,101 to Geissler discloses the use of an in-line trap which is set to collect the first few millilitres (ml) of blood drawn from a donor. It is manually operable by pulling on the blood line to cause the remainder of blood flowing from the donor to pass to the bag-set. Its stated purpose is to capture tissue thromboplastin generated by the trauma of vein penetration. However, the device is not fool-proof. If the phlebotomist pulls on the blood line too early, the tissue thromboplastin will flow to the collection bag; if the blood line is not pulled sufficiently firmly to close the trap, the blood in the trap will mix with blood flowing to the collection bag. Moreover, since operation of this device depends upon a sliding joint between the blood-line in the body of the trap, it is not a closed system. It is possible that bacteria could find their way into the trap, and for blood to be transferred out of the trap, through the sliding joint.
Though Geissler makes no comment regarding the potential danger of contamination via a skin-plug, the trap of U.S. Pat. No. 4,506,101 will not offer a certain safeguard against this danger. First, as noted above, it is not fool-proof in that blood in the trap can mix with blood flowing to the bag-set if the trap is not operated correctly. Second, even if the trap is operated correctly, it is quite possible that a skin plug contained in the first few milliliters of blood will flow straight into the open end of the blood line which is directly opposite the inlet to the trap. Moreover, Geissler""s trap is of no value in providing blood samples because there is no way of accessing the blood collected by the trap, nor was that intended as the volume of the trap is far too small to provide the samples normally required from each donor (30 to 40 ml).
In Japanese patent application No. 09028265 (Publication No. 10211274), Terumo Corp teaches the use of a first in-line frangible seal in the blood line between the IV needle and the blood bag and a second in a branch sample line connected to the blood line upstream of the first connector. Each seal blocks its respective line until it is broken by external manipulation of the line. After the IV needle is inserted in the donor, the second seal is broken to allow blood to flow into the sample line for removal via a sample port connected to the sample line. The first seal is then broken to permit flow of blood to the collection bags. While this procedure is intended to ensure that the initial blood flow is directed to the sample tube, portion of that flow (perhaps containing the skin plug) will fill the blood line upstream of its seal and then be conveyed to the blood pack after the first seal is broken. If samples are taken during blood collection, the system will be opened; if samples are taken after collection has been completed and the blood line sealed, the procedure will be prolonged (as with the conventional procedure).
Finally, it will be appreciated that, whilst the present invention is concerned with blood sampling in association with the collection of blood from donors, systems are known for collecting samples of arterial blood during medical procedures that employ indwelling catheters for infusing saline solutions or medication and that attempt to minimise blood spillage or waste during sample collection. For example, U.S. Pat. No. 5,772,608 to Dhas discloses a system for infusing medication into the artery of a patient that uses manually operable valves to employ the patient""s arterial blood pressure to flush the medication from the line into a waste bag before blood samples are taken from the line via a normal sampling port. The issue of contamination of collected blood by skin plugs and is the like are clearly not relevant in such procedures.
The present invention involves the use of a multi-port/multi-position valve in the blood line from the needle to the collection bag that can be operated to first connect the needle line to a branch line at the start of the blood collection procedure and then connect the needle line to the bag line for blood collection. The arrangement is preferably such as to ensure that any skin plug is diverted with the initial blood flow to the branch line. Preferably, the branch line itself comprisesxe2x80x94or is connected toxe2x80x94a sealed container or pouch for holding sample blood. The branch line may therefore be referred to below as the xe2x80x98sample linexe2x80x99.
The multi-port valve preferably seals-off the bag-line while the sample blood is collected and seals off the sample line while main blood collection takes place. This ensures that any skin plug and thromboplastin is captured by the sample container and allows samples for analysis to be drawn from the sample container (using conventional techniques) while blood collection takes place. Thus, the likelihood of pack contamination is reduced and the time taken for the procedure is shortened.
As between 30 and 60 mIs of blood is normally required for a normal set of samples during blood collection from a single donor, it will be seen that there is plenty of initial blood flow to carry any skin plug into the sample container and that, furthermore, there is no possibility that the skin plug can find its way from the sample line into the blood line to the bag-set.
The valve may be fitted with safety means to ensure that (i) the initial blood flow cannot be inadvertently transferred to the bag line, (ii) the bag-line and the sample line can never be interconnected and/or (iii) neither the bag line nor the sample line can be reconnected to the needle line after blood flow to the bag set has been terminated by use of the valve.
More than one sample container may be employed and clamps or similar devices may be used to direct sample blood flow to each in turn until sufficient sample blood has been collected. This allows the initial blood flow (containing any skin plug) to wash any anticoagulant or saline fill in the needle and sample lines into the first sample container so that blood directed to subsequent sample containers will be free of such diluents.
If the sample container(s) is rigid or semi-rigid, some means of allowing air therein to escape as it fills will be required. Filtered vents with automatic shut-offs for this purpose are well known in the art. Preferably, however, the sample container is a small flexible lay-flat pouch substantially free of air, (not unlike the bags of the collection set) which can expand as blood flows into it. Such a sample pouch can be divided into a plurality of interconnected sub-pouches that are collectively or individually capable of being removed from the sample line for later access. Preferably, the volume of blood taken for samples in this way should be controllable by the phlebotomist in a simple manner; for example, by folding over and dipping the pouch or closing off one or more of the sub-pouches or containers. Most preferably, the volume of blood collected for samples may be controlled by the use of the valve operated manually by the phlebotomist, though the use of such a valve may be in addition to control of the volume of the sample collection container(s).
For convenience, the sample container will be referred to below as a xe2x80x98pouchxe2x80x99 though it will be appreciated from the above that such a container is not the only one envisaged.
The valve means may be a rotary or linear valve, or a combined rotary and linear valve. It is preferably such that it can only be operated in one direction so that (i) the sample pouch cannot be re-connected to the blood line after flow to the collection bag has been closed off, and (ii) the bag set cannot be reconnected to the blood line after the valve has been placed in the xe2x80x98off positionxe2x80x99 at the end of blood collection. However, it is also desirable (but not essential) for the valve to be arranged to allow anticoagulant to be fed to the bag set during manufacture so that the valve can be fitted to the blood lines before filling and, of course, prior to sterilisation.
The valve means may incorporate a sample port for the connection of a conventional sampling syringe, vacuum phial or other sampling device, thereby saving the need for a Y-connector in the line to the sample pouch. For example, the port may comprise a pre-slit septum device of the type disclosed in WO 90/12606 by Baxter International Inc. The valve actuator means and the sample port may be fixed together so that the sample port may be used to manipulate the valve.
The valve may be anchored to the arm of the donor by a suitable strap or the like. Conveniently, this may be a wrist strap and the valve can be attached to the strap by Velcro or the like. The immobilisation of the blood line in this way is an added advantage for the comfort of the donor and may avoid the need for the use of a conventional adhesive strip for this purpose. The strap also ensures that the movement of the sample pouch necessary for operation of the sample port and vacuum phials cannot affect the needle line or the blood collection line.
As already indicated, the valve may provide a connector for the sample port or a tube could be led from the valve for connection to the sample port. Alternatively, a tube having a sample port (or a connector for such a port) on one end may be connected by its other end to the bottom of the sample pouch. In that case, it is preferable to attach the sample port itself to the top of the sample pouch so that it does not hang down and is located at a convenient angle for use.